1. Field of the Invention
This invention relates to granular detergent additive compositions containing a bleach active compound and an activator for the bleach active compound. More particularly, this invention relates to a method for intimately mixing two powdery mutually reactive ingredients: a bleach active compound and an activator therefor, with an inert, normally solid binder, in the form of solid particles or granules, and to the resulting particulate bleach active detergent additive composition.
2. Discussion of the Prior Art
The difficulties and problems encountered when attempting to incorporate in a detergent composition detergent additive ingredients, such as fluorescers, germicides, anti-tarnishing agents, enzymes, perfumes, bleach active compounds, bleach activator compounds, etc., which additives are either reactive with each other or with other components of the composition or which are liable to decompose, discolor, separate out or aggregate, have been recognized in the art.
One proposal for solving this problem has been provided in British Patent Specification No. 1,204,123 to Unilever, Ltd. According to this proposal, the detergent additive is in the form of granules made by mechanical working of a mixture of an organic extrudable solid and the additive, with the additive being dispersed throughout the granules. The additive-containing granules may then be mixed with the remaining ingredients of the detergent composition.
According to U.S. Pat. No. 4,399,049 to Gray and Harris, the dispersibility or dissolution characteristics of the granular additives of the above-mentioned British Patent to Unilever are improved by a detergent additive composition in the form of an extrudate comprising by weight thereof:
(a) from about 75% to about 95% of particulate, infusible solids having a particle size distribution such that at least about 50% thereof passes a 250 micrometer screen and comprising storage-sensitive detergent additive material, and
(b) from about 5% to about 25% of ethoxylated nonionic surfactant melting in the range from about 20.degree. C. to about 60.degree. C., the composition being prepared by mixing the particulate infusible solids and ethoxylated nonionic surfactant in liquid form to form a substantially homogeneous friable mass, and mechanically extruding the friable mass by means of a screw with radial discharge through an apertured screen to form extrudate in the form of elongate particles having an average lateral dimension in the range from 0.5 millimeters to 2 millimeters, and an average longitudinal dimension in the range from about 1 mm to about 6 mm.
The storage-sensitive detergent additive material can be a unifunctional or multifunctional material selected from bleaching auxiliaries, photoactivators, fluorescers, dyes, perfumes, germicides, enzymes, suds controllers, fabric conditioners and the like. Preferred detergent additive materials are organic peroxyacid bleach precursors also called bleach activators.
As described in this prior art, the above and other attempts to improve the storage-stability characteristics of detergent additive materials such as bleach activators has involved protection of the additive material from its "hostile" environment by agglomerating, coating or encapsulating the material with an organic coating material which can readily form a substantially cohesive and continuous plastic matrix in which the additive material can be embedded.
While the satisfactory improvements in storage-stability characteristics have been achieved with the above-mentioned techniques, it has been found that in the case where the detergent additive is a bleach activator, the activity or action of the detergent additive is often impaired by being embedded within the organic matrix, even where the dispersibility or dissolution characteristics of the binder are good.
Accordingly, the present invention provides detergent additive compositions having improved bleaching effectiveness, especially at low-wash water temperatures. More particularly, the invention provides detergent additive granules in which both of the oxygen-containing bleach and bleach activator are incorporated as a result of which improved stain removal (bleach activity) is achieved without impairing the storage-characteristics of the detergent additive compositions or of the full detergent compositions to which they are added. The invention also provides the improved detergent compositions which include the detergent additive compositions as well as the method for preparing the granular detergent additive compositions.